The growth in the use of personal computers, word processors and other similar types of office equipment has resulted in a corresponding growth in the use of the magnetic disc as a means of storing information generated by, entered into, or retrieved from such equipment. These discs, generally called "floppy discs" are thin, flexible, and coated with a sensitive magnetic material. Consequently, they must be protected from direct handling by equipment operators or from contacting physical parts of the machinery other than those portions which either transfer information onto or retrieve it from such discs.
The current most common form of disc protection generally comprises a flat envelope, usually made of some sort of paper or plastic material, into which the disc is inserted. The envelope generally has several openings in it e.g., one in the center for permitting the mechanical disc drive to engage the disc, and a second opening spaced from the center through which the magnetic surface of the disc can be exposed so that the computer, word processor or other machine can read from or write to the disc.
Floppy discs most commonly are produced in two sizes, 51/4" and 8". The construction and use of both is generally very similar and often identical.
As expected in the generating, maintaining and retrieval of stored information of any type in any medium, there often exists circumstances when information stored on a floppy disc should be permanently maintained relatively secure from inadvertent erasure or when material formerly stored should desirably be erased so that the disc may be reused rather than discarded. These opposite functions are sometimes referred to as "read-only" or "write-protect" functions and "write" or "write-to-disc" functions, respectively. In either case, the object is to provide a disc upon which fresh information can be recorded and stored or a disc from which stored information can continually be retrieved but which cannot be erased or written over. As is typical of most magnetic recording mediums, recording over existing materials stored on a disc effectively erases those existing materials, whether or not erasure is intended.
For such reasons, floppy disc envelopes typically include a notch in one folded side edge of the outer envelope into which a mechanical device can fall or through which an optical signal may pass in order to either accomplish the transfer of material onto the disc or to prevent material from being transferred onto the disc. In one common embodiment, the notch allows the machine to record on the disc and when the notch is covered or absent the disc will "read only" or be "write-protected", i.e. material can be retrieved from the disc but none can be recorded onto it.
In order to use discs for both write and write-protect purposes, small pieces of special adhesive tape have commonly been used to cover the notches and thereby provide a write-protect function. Although once in place the tape provides write-protection, the tapes are messy, nonadjustable, difficult to remove, and leave an adhesive residue. Additionally, removing the tape requires more than usual handling of the fragile disc, lessening its effective life. Over longer periods of time, the adhesive properties on the tape can deteriorate so that the tapes loosen and stick to other discs in storage or loosen in the machine, thereby fouling the disc drive. Some tapes are overly sensitive to humidity and will not remain in place long enough under certain humidity conditions.
One attempted solution to this problem has been to develop a solid insert which would cover the notch in a floppy disc envelope and thereby provide a write-protect function. One recent example is given by Fann in U.S. Pat. No. 4,521,820 in which one end of a plastic strip is inserted into the notch and the other end remains exposed outside the envelope where it can be seen and grasped by an operator to effect removal. There are, however, several disadvantages to this device. First, nothing other than friction serves to hold the device permanently inserted in the envelope. Secondly, since the strip is smaller than the slot in the envelope into which it fits, nothing serves to guide the strip into the proper position in the slot. Third, the device can only be inserted from one direction, a disadvantage in certain handling applications. Finally, the device never forms a permanent part of the envelope.
It is thus an object of the present invention to provide a casing for a magnetic recording disc which includes an envelope which is characterized by a write-protect capability, and which overcomes the aforementioned disadvantages of other write-protect methods and devices.
It is a further object of this invention to provide a casing of the described type, and which includes a slideably mounted write-protect strip which is adapted to provide selective write and write-protect functions as the user wishes, and which also has provision for facilitating its sliding movement and for precluding inadvertent movement of the strip once it is in place in the envelope.
It is another object of the invention to provide a write-protect strip which can be moved to and maintained at respective write and write-protect positions defined by an interengagement between the envelope and the strip.